The relationship of graded, dietary zinc intake levels and an injected zinc load to the synthesis of a low molecular weight zinc binding protein will be investigated in the liver, kidney and intestinal mucosa of rats. The proteins that bind zinc will be measured with the use of Zn65 administered in vivo and/or in vitro. The low molecular weight zinc binding protein from the tissues of interest will be isolated, purified and characterized from both rat and porcine sources. Comparisons will be made to metallothione in a known zinc binding protein. The mechanisms of zinc binding protein synthesis will be investigated using the incorporation of C14-labeled amino acids and Zn65. These nuclides are measurable simultaneously by differential liquid scintillation counting. The use of actinomycin D and cycloheximide coupled with C14-amino-acid and Zn65 incorporation will ascertain the level of protein synthesis at which Zn plus 2 exerts its influence on zinc binding protein synthesis. Combination sequential in vivo and in vitro incubation studies with both H3 and C14-amino acids will establish the inducibility of the low molecular weight zinc binding protein. The influence of zinc on the synthesis of ZnBP-specific RNA species will be investigated via density gradient centrifugation. The data obtained will be related to the possible role of this low molecular weight zinc binding protein in zinc absorption, metabolism and storage as well as zinc toxicity.